Step wise refinement

1. Step wise refinement • This time implement your solution by using high level methods you wish you had. • Then implement those methods using simpler high level methods you wished you had. • Continue in this manner until you are invoking the primitive methods to implement you higher level methods.

2. Sample Problem • Design a Robot to lay Beepers in a overpass walkway pattern. • Start Robot at 2,3, ends at 2,14 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 9 10 11 12 13

3. Step One • Implement the task method using whatever magical methods I want. public void task() { climbUpStairs(); walkAcrossTop(); climbDownStairs(); } • Notice that each new word begins with a capital letter

4. Step Two • Implement those magical methods. • First implement climbUpStairs public void climbUpStairs() { moveTwo(); turnRight(); moveThree(); }

5. Step Three • Now implement those magical methods. • moveTwo(), turnRight() and moveThree(); public void moveTwo(){ move(); move(); } public void moveThree(){ moveTwo(); move(); } public void turnRight(){ you’ve seen already }

6. Step Four • Test climbUpStairs • In the task method, Comment out: walkAccrossTop and climbDownStairs as shown below: public void task() { climbUpStairs(); // walkAcrossTop(); // climbDownStairs(); } And execute MainDriver1. Does climbUpStairs work as desired? If not fix it!

7. Fix climbUpStairs public void climbUpOneStair() { turnLeft(); moveTwo(); turnRight(); moveTwo(); } public void climbUpStairs() { climbUpOneStair(); climbUpOneStair(); climbUpOneStair(); }

8. Step Five • Implement walkAcrossTop • Test walkAcrossTop by uncommenting the call to walkAcrossTop in the task method as shown below public void task() { climbUpStairs(); walkAcrossTop(); // climbDownStairs(); }

9. Step Six • Implement climbDownStairs • Test climbDownStairs by uncommenting the call to climbDownStairs in the task method as shown below public void task() { climbUpStairs(); walkAcrossTop(); climbDownStairs(); }

10. Your final Karel Task • Time for one last karel assignment before returning to Alice! • See worksheet